Characteristics of pellets (pellet size distribution, their mean diameter, density, hardness, friability, repose angle, Hausner ratio, and drug dissolution profiles) prepared by axial and radial extrusion/spheronization were examined in this experimental study. The formulation consisted of binary mixtures of theophylline, a drug slightly soluble in water, and Avicel® CL 611 as an excipient. Different characteristics were found in the samples prepared using the different extrusion dies: the axially situated extrusion die produces the pellets of higher hardness and density, and slower dissolution profiles. Differences in drug dissolution profiles should be considered, nevertheless they are not significant. All pellet samples showed low friability and excellent flow properties.

        Key words: pellets – theophylline – Avicel® CL 611 – extrusion/spheronization – axial extrusion – radial extrusion